scholarly journals Long-term changes in the water temperature of rivers in Latvia

2016 ◽  
Vol 70 (2) ◽  
pp. 78-87 ◽  
Author(s):  
Inese Latkovska ◽  
Elga Apsīte
Keyword(s):  
Water Temperature ◽  
Kendall Test ◽  
Maximum Temperature ◽  
Small Rivers ◽  
Positive Trend ◽  
Annual Maximum ◽  
Monitoring Period ◽  
Time Period ◽  
Maximum Water Temperature ◽  
Maximum Water

Abstract The study describes the trends of monthly mean water temperature (from May to October) and the annual maximum water temperature of the rivers in Latvia during the time period from 1945 to 2000. The results demonstrated that the mean water temperatures during the monitoring period from May to October were higher in the largest rivers (from 13.6 °C to 16.1 °C) compared to those in the smallest rivers (from 11.5 °C to 15.7 °C). Similar patterns were seen for the maximum water temperature: in large rivers from 22.9 °C to 25.7 °C, and in small rivers from 20.8 °C to 25.8 °C. Generally, lower water temperatures occurred in rivers with a high groundwater inflow rate, for example, in rivers of the Gauja basin, in particular, in the Amata River. Mann-Kendall test results demonstrated that during the monitoring period from May to October, mean water temperatures had a positive trend. However, the annual maximum temperature had a negative trend.

The increasing of maximum lake water temperature in lowland lakes of central Europe: case study of the Polish Lakeland

2019 ◽  
Vol 55 ◽  
pp. 6 ◽  
Author(s):  
Mariusz Ptak ◽  
Mariusz Sojka ◽  
Michał Kozłowski
Keyword(s):  
Cluster Analysis ◽  
Water Temperature ◽  
Warming Trend ◽  
Maximum Temperature ◽  
Average Value ◽  
Temperature Trends ◽  
Air Temperatures ◽  
Maximum Water Temperature ◽  
Maximum Water ◽  
Maximum Temperatures

The paper presents the results of time-related changes in maximum temperatures in lakes. The analysis was carried out on the basis of 9 lakes located in the northern part of Poland. The analysis was based on daily water and air temperatures in the period 1971–2015. Mann–Kendall's and Sen's tests were applied to determine the directions and rates of change of maximum air and water temperatures. The average increase of maximum water temperature in analysed lakes was found to be 0.39 °C dec–1, while the warming trend of the maximum air temperature was 0.48 °C dec–1. Cluster analysis (CA) was used to group lakes characterised by similar changes of maximum water temperature. The first group included five lakes in which the values of the maximum temperature trends were 0.41 °C dec–1. In the second cluster the average value of maximum water temperature increase was smaller than in the first cluster (0.36 °C dec–1). Comparing the results of cluster analysis with morphometric data show that in the first cluster lakes are having a greater average depth, maximum depth and water transparency in comparison to the lakes of the second cluster.

Effects of wildfire on stream temperatures in the Bitterroot River Basin, Montana

2011 ◽  
Vol 20 (2) ◽  
pp. 240 ◽  
Author(s):  
Shad K. Mahlum ◽  
Lisa A. Eby ◽  
Michael K. Young ◽  
Chris G. Clancy ◽  
Mike Jakober
Keyword(s):  
Water Temperature ◽  
River Basin ◽  
Natural Disturbance ◽  
Maximum Temperature ◽  
Aquatic Species ◽  
Reference Sites ◽  
Temperature Changes ◽  
High Severity ◽  
Maximum Water Temperature ◽  
Maximum Water

Wildfire is a common natural disturbance that can influence stream ecosystems. Of particular concern are increases in water temperature during and following fires, but studies of these phenomena are uncommon. We examined effects of wildfires in 2000 on maximum water temperature for a suite of second- to fourth-order streams with a range of burn severities in the Bitterroot River basin, Montana. Despite many sites burning at high severity, there were no apparent increases in maximum water temperature during the fires. One month after fire and in the subsequent year, increases in maximum water temperatures at sites within burns were 1.4–2.2°C greater than those at reference sites, with the greatest differences in July and August. Maximum temperature changes at sites >1.7 km downstream from burns did not differ from those at reference sites. Seven years after the fires, there was no evidence that maximum stream temperatures were returning to pre-fire norms. Temperature increases in these relatively large streams are likely to be long-lasting and exacerbated by climate change. These combined effects may alter the distribution of thermally sensitive aquatic species.

scholarly journals Trends in the Maximum, Mean, and Low Flows of Turkish Rivers

2005 ◽  
Vol 6 (3) ◽  
pp. 280-290 ◽  
Author(s):  
H. K. Cigizoglu ◽  
M. Bayazit ◽  
B. Önöz
Keyword(s):  
Trend Analysis ◽  
Kendall Test ◽  
T Test ◽  
Precipitation Trend ◽  
Annual Maximum ◽  
Low Flows ◽  
Time Period ◽  
Southern Turkey ◽  
The Mean ◽  
Maximum Flows

Abstract In this study the existence of trend in maximum, mean, and low flows of Turkish rivers has been investigated. The data consisted of the daily mean flows of nearly 100 flow stations in 24 hydrological regions of Turkey. Trend analysis has been carried out using the parametric t test and nonparametric τ (Mann–Kendall) test. Both tests have been applied to annual maximum, mean, 1-day, and 7-day low flows. Trend existence was detected in the majority of rivers in western and southern Turkey and in some parts of central and eastern Turkey. Trends in mean and low flows were more common compared with maximum flows. Except at a few stations, flows showed a decreasing trend. In the time period of the last 30–60 yr, statistically significant decrease was found especially in the mean and low flows (and in some of the maximum flows) in western, central, and southern parts of Turkey. Such trends were not observed in other regions. These results are in agreement with those of the precipitation trend studies in Turkey.

Homogeneity Evaluation of Historical Rainfall and Temperature Series in Mato Grosso

2019 ◽  
pp. 1-7
Author(s):  
Elizangela Selma da Silva ◽  
José Holanda Campelo Júnior ◽  
Francisco De Almeida Lobo ◽  
Ricardo Santos Silva Amorim
Keyword(s):  
Trend Analysis ◽  
Minimum Temperature ◽  
Statistical Tests ◽  
Kendall Test ◽  
Maximum Temperature ◽  
Data Series ◽  
Positive Trend ◽  
Mato Grosso ◽  
Temperature Climate ◽  
Precipitation And Temperature

The homogeneity investigation of a series can be performed through several nonparametric statistical tests, which serve to detect artificial changes or non-homogeneities in climatic variables. The objective of this work was to evaluate two methodologies to verify the homogeneity of the historical climatological series of precipitation and temperature in Mato Grosso state. The series homogeneity evaluation was performed using the following non-parametric tests: Wald-Wolfowitz (for series with one or no interruption), Kruskal-Wallis (for series with two or more interruptions), and Mann-Kendall (for time series trend analysis). The results of the precipitation series homogeneity analysis from the National Waters Agency stations, analyzed by the Kruskal-Wallis and Wald-Wolfowitz tests, presented 61.54% of homogeneous stations, being well distributed throughout Mato Grosso state, whereas those of the trend analysis allowed to identify that 87.57% of the rainfall-gauging stations showed a concentrated positive trend, mainly in the rainy season. Out of the conventional stations of the National Institute of Meteorology of Mato Grosso, seven were homogeneous for the precipitation variable, five for maximum temperature and four stations were homogeneous for minimum temperature. For the trend analysis in the 11 stations, positive trends of random nature were observed, suggesting increasing alterations in the analyzed variables. Therefore, the trend analysis performed by the Mann-Kendall test in the precipitation, and maximum and minimum temperature climate series, indicated that several data series showed increasing trends, suggesting a possible increase in precipitation and temperature values over the years. The results of the Kruskal-Wallis and Wald-Wolfowitz tests for homogeneity presented more than 87% of homogeneous stations.

scholarly journals Cuantificación e interpolación de tendencias locales de temperatura y precipitación en zonas alto andinas de Cundinamarca y Boyacá (Colombia)

2010 ◽  
Vol 11 (2) ◽  
pp. 173 ◽  
Author(s):  
Edwin Rojas ◽  
Blanca Arce ◽  
Andrés Peña ◽  
Francisco Boshell ◽  
Miguel Ayarza
Keyword(s):  
Production Systems ◽  
Hydrological Cycle ◽  
Kendall Test ◽  
Maximum Temperature ◽  
Positive Trend ◽  
Weighted Interpolation ◽  
Weather Patterns ◽  
Statistical Confidence ◽  
Temperature And Precipitation ◽  
Inverse Distance Weighted Interpolation

<p>El cambio en el patrón climático global no sólo afecta la temperatura, sino el ciclo hidrológico con mayores variaciones en los ambientales locales. Con el fin de cuantificar las tendencias de temperatura máxima, mínima y precipitación media, se realizó un análisis no-paramétrico de las series de tiempo de 31 estaciones meteorológicas ubicadas en zonas alto andinas de Cundinamarca y Boyacá, con registros de 1985 a 2008. Se calcularon las tendencias de cambio de las variables climáticas para cada una de las estaciones mediante el método de estimación de pendiente de Sen y se utilizó la prueba de Mann- Kendall para determinar el nivel de confianza de dichas tendencias. La temperatura máxima mostró tendencias positivas con niveles de confianza significativa (&gt;90%) en la mayoría de estaciones climáticas. Para la temperatura mínima, la tendencia positiva fue detectada en menor número de estaciones pero con mayores niveles de confianza estadística (12 estaciones superaron el 95%). La precipitación mostró tendencias significativas (&gt;90%) sólo en siete de las 31 estaciones analizadas (seis de ellas fueron positivas y una negativa). Se utilizó el método de interpolación de distancia inversa ponderada (IDW) para generar los mapas de la distribución espacial de las tendencias. Mediante validación cruzada se encontró que el IDW tiene un mejor ajuste para la precipitación que para la temperatura. Se concluye que el cambio climático tiene manifestaciones muy locales en términos del comportamiento de las temperaturas y la precipitación para la zona de estudio, lo que podría generar impactos específicos sobre los sistemas productivos de la región.</p><p> </p><p><strong>Quantization and interpolation of local trends in temperature and precipitation in the high Andean areas of Cundinamarca and Boyaca (Colombia)</strong></p><p>Change in global weather patterns affects not only temperature, but also the hydrological cycle with greater variations in local environments. In order to quantify trends in maximum temperature and minimum and average precipitation, we performed a nonparametric analysis of time series of 31 meteorological stations located in the high Andes of Cundinamarca and Boyaca, with records from 1985 to 2008. We calculated the changing trends of climatic variables for each of the stations with the Sen slope estimator and we used the Mann-Kendall test to determine the confidence level of such trends. The maximum temperature showed positive trends with significant confidence levels (&gt; 90%) in most seasons. For the lowest temperature, the positive trend was detected in fewer stations but with higher levels of statistical confidence (12 stations exceeded 95%). Rainfall showed significant trends (&gt; 90%) in only seven of the 31 stations analyzed (six of them were positive and one negative). We used the method of inverse distance weighted interpolation (IDW) to generate maps of the spatial distribution of the trends. Cross validation found that IDW has a better fit for precipitation than for temperature. We conclude that climate change manifests very local expressions in terms of the behavior of temperatures and precipitation for the study area, which could lead to specific impacts on production systems in the region.</p>

scholarly journals What causes cooling water temperature gradients in forested stream reaches?

2014 ◽  
Vol 11 (6) ◽  
pp. 6441-6472 ◽  
Author(s):  
G. Garner ◽  
I. A. Malcolm ◽  
J. P. Sadler ◽  
D. M. Hannah
Keyword(s):  
Water Temperature ◽  
Water Column ◽  
Stream Temperature ◽  
Temperature Gradients ◽  
Daily Maximum ◽  
Net Energy ◽  
Net Radiation ◽  
Maximum Water Temperature ◽  
Maximum Water ◽  
Energy Gains

Abstract. Previous studies have suggested that shading by riparian vegetation may reduce maximum water temperature and provide refugia for temperature sensitive aquatic organisms. Longitudinal cooling gradients have been observed during the daytime for stream reaches shaded by coniferous trees downstream of clear cuts, or deciduous woodland downstream of open moorland. However, little is known about the energy exchange processes that drive such gradients, especially in semi-natural woodland contexts, and in the absence of potentially confounding cool groundwater inflows. To address this gap, this study quantified and modelled variability in stream temperature and heat fluxes along an upland reach of the Girnock Burn (a tributary of the Aberdeenshire Dee, Scotland) where riparian landuse transitions from open moorland to semi-natural forest. Observations were made along a 1050 m reach using a spatially-distributed network of ten water temperature micro-loggers, three automatic weather stations and >200 hemispherical photographs, which were used to estimate incoming solar radiation. These data parameterised a high-resolution energy flux model, incorporating flow-routing, which predicted spatio-temporal variability in stream temperature. Variability in stream temperature was controlled largely by energy fluxes at the water column–atmosphere interface. Predominantly net energy gains occurred along the reach during daylight hours, and heat exchange across the bed-water column interface accounted for <1% of the net energy budget. For periods when daytime net radiation gains were high (under clear skies), differences between water temperature observations decreased in the streamwise direction; a maximum difference of 2.5 °C was observed between the upstream reach boundary and 1050 m downstream. Furthermore, daily maximum water temperature at 1050 m downstream was ≤1°C cooler than at the upstream reach boundary and lagged the occurrence of daily maximum water temperature upstream by >1h. Temperature gradients were not generated by cooling of stream water, but rather by a combination of reduced rates of heating in the woodland reach and advection of cooler (overnight and early morning) water from the upstream moorland catchment. Longitudinal thermal gradients were indistinct at night and on days when net radiation gains were low (under over-cast skies), thus when changes in net energy gains or losses did not vary significantly in space and time, and heat advected into the reach was reasonably consistent. The findings of the study and the modelling approach employed are useful tools for assessing optimal planting strategies for mitigating against ecologically damaging stream temperature maxima.

Monotonic Trend Analysis of Temperature Series over Mandya City, Karnataka

2021 ◽  
Vol 9 (VII) ◽  
pp. 1530-1535
Author(s):  
Madhusudhan M S
Keyword(s):  
Climate Change ◽  
Trend Analysis ◽  
Agricultural Sector ◽  
Kendall Test ◽  
Temperature Series ◽  
Maximum Temperature ◽  
Positive Trend ◽  
Significance Level ◽  
Monotonic Trend ◽  
Indirect Impacts

Climate change is mostly driven by global warming. Climate change is one of the most critical long-term development issues, particularly for developing countries like India. India is one of the world's most climatically diverse countries, making it sensitive to climatic change and impacting the livelihoods of millions of people who rely on agriculture. Temperature and its fluctuation have direct and indirect impacts on crop development in the agricultural sector. Understanding the temperature and its variability in a changing environment would aid in improved decision-making and suggest feasible adaption strategies. The present study focuses on temperature trend analysis in Mandya city, Karnataka, India. The analysis was carried out through the non-parametric Mann-Kendall test and Sen's slope estimator. The findings demonstrate that, there has been a rising trend in temperature in the study area over the last 30 years as a result of climate change. From the analysis, there is a significant positive trend for all the seasons considered for the significance level of 90%, 95% and 99%. The magnitude of the increasing trend will be in the range of 0.46 °C/year for the average time series. Also, there will be an average increase of 0.07 °C/year for the various scenarios considered in Mandya city for the Maximum temperature series.

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